title: RhoG protein regulates platelet granule secretion and thrombus formation in mice.
abstract: Rho GTPases such as Rac, RhoA, and Cdc42 are vital for normal platelet function, but the role of RhoG in platelets has not been studied. In other cells, RhoG orchestrates processes integral to platelet function, including actin cytoskeletal rearrangement and membrane trafficking. We therefore hypothesized that RhoG would play a critical role in platelets. Here, we show that RhoG is expressed in human and mouse platelets and is activated by both collagen-related peptide (CRP) and thrombin stimulation. We used RhoG(-/-) mice to study the function of RhoG in platelets. Integrin activation and aggregation were reduced in RhoG(-/-) platelets stimulated by CRP, but responses to thrombin were normal. The central defect in RhoG(-/-) platelets was reduced secretion from α-granules, dense granules, and lysosomes following CRP stimulation. The integrin activation and aggregation defects could be rescued by ADP co-stimulation, indicating that they are a consequence of diminished dense granule secretion. Defective dense granule secretion in RhoG(-/-) platelets limited recruitment of additional platelets to growing thrombi in flowing blood in vitro and translated into reduced thrombus formation in vivo. Interestingly, tail bleeding times were normal in RhoG(-/-) mice, suggesting that the functions of RhoG in platelets are particularly relevant to thrombotic disorders.
authors.affiliation: School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom.
authors.forename: Robert
authors.initials: R
authors.lastname: Goggs
authors.affiliation: School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Harper
authors.affiliation: School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Pope
authors.affiliation: School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom.
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Savage
authors.affiliation: School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Williams
authors.affiliation: School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Mundell
authors.affiliation: Proteomics Facility, University of Bristol, Bristol BS8 1TD, United Kingdom.
authors.forename: Kate J
authors.initials: KJ
authors.lastname: Heesom
authors.affiliation: School of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Bass
authors.affiliation: School of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom.
authors.forename: Harry
authors.initials: H
authors.lastname: Mellor
authors.affiliation: School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom. Electronic address: a.poole@bris.ac.uk.
authors.forename: Alastair W
authors.initials: AW
authors.lastname: Poole
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D001777:Blood Coagulation; D001792:Blood Platelets / Q000201:enzymology* / Q000473:pathology; D002352:Carrier Proteins / Q000494:pharmacology; D005260:Female; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D006490:Hemostatics / Q000494:pharmacology; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D010455:Peptides / Q000494:pharmacology; D015539:Platelet Activation / Q000187:drug effects / Q000235:genetics; D022142:Secretory Vesicles / Q000235:genetics / Q000378:metabolism*; D013917:Thrombin / Q000378:metabolism / Q000494:pharmacology; D013927:Thrombosis / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D020741:rho GTP-Binding Proteins
chemical_list: D002352:Carrier Proteins; D006490:Hemostatics; D010455:Peptides; C489577:Rhog protein, mouse; C435908:collagen-related peptide; D000244:Adenosine Diphosphate; D013917:Thrombin; D020558:GTP Phosphohydrolases; D020741:rho GTP-Binding Proteins
keywords: Platelets; Proteomics; Rho GTPases; Secretion; Thrombosis; Transgenic Mice